The present invention relates to an audio signal discriminator circuit for use in automatic telephone recording apparatus.
In automatic telephone recording apparatus, it is the practice to start its recording operation in response to an incoming telephone call signal and stop the operation at the end of the call signal by the use of an audio signal discriminator circuit having a function of distinguishing audio signals from other signals such as dialed tones, beep tones, howler tones, etc. incoming from the telephone line.
An audio signal discriminator circuit has been proposed in the art in which the statistical property of audio signals is utilized so that audio signals are distinguished from other signals in accordance with the duration of the signal kept in a range higher than a predetermined level. Such an apparatus, however, is not free from misoperations.